Zinc oxide thin films having high transparency towards visible light are used in a broad range of applications such as photocatalyst films, UV cutting film, infrared reflective film, CIGS, buffer layers of organic thin-film solar cells, electrode films of dye-sensitized solar cells, antistatic films, thin-film transistors, compound semiconductor light-emitting devices, phosphor elements, antibacterial/deodorant films, piezoelectric films, varistor films, and plating films (Non Patent Literature 1).
Although various methods are known as production methods of transparent zinc oxide thin films (Non Patent Literature 2), production by coating, which boasts high productivity and low film production, costs is preferred herein, on account of the high film formation rates achieved, and also on account of equipment simplicity, in that it is not necessary to use a vacuum vessel.
Coating methods include for instance spin coating (Patent Literature 1), dip coating (Non Patent Literature 3), spray pyrolysis (Non Patent Literature 4) and the like.
A zinc oxide thin film is obtained through heating, at a substrate temperature of 350° C. or higher, after coating by spin coating, dip coating or spray pyrolysis.
Plastic substrates have come to be used as substrates of transparent zinc oxide thin films. Accordingly, heating during formation of the transparent zinc oxide thin film must be carried out at or below the heat resistance temperature of the plastic substrate. In the above spin coating, dip coating or spray pyrolysis methods, however, it is not possible to obtain a transparent zinc oxide thin film through heating at or below the heat resistance temperature of a plastic.
Therefore, studies by the inventors led to the finding of a method for forming a transparent zinc oxide thin film also at a temperature of 300° C. or lower, through the use of a solution containing a partial hydrolysate of dialkylzinc, obtained through reaction of dialkylzinc and water (Patent Literature 2).    [PTL 1] Japanese Patent Application Publication No. H07-182939    [PTL 2] Japanese Patent Application Publication No. 2010-254481 (Japanese Patent No. 5546154)    [NPL 1] “Zinc Oxide Transparent Conductive Films: Towards Next-Generation Displays” Hakusui Tech Co., Ltd. General magazine, Info, Volume 13 (2005) p1    [NPL 2] Technology of Transparent Conductive Films, edited by the 166th Committee on Photonic and Electronic Oxide Materials of the Japan Society for the Promotion of Science, Second edition (Revised), (2006) p 165 to 173    [NPL 3] Y. Ohya et al, J. Mater. Sci., 29 (1994) 4099    [NPL 4] J. Aranovich et al, J. Vac. Sci. Technol., 4 (1979) 16 PLT 1 to 2 and NPL 1 to 4 are expressly incorporated herein by reference in their entirety.